1. Field of the Invention
The present invention relates to a semiconductor device fabrication method and, more particularly, to a semiconductor device fabrication method which improves a method of forming a nanoparticle oxide thin film to be used as an interlayer insulator with a low dielectric constant.
2. Description of the Related Art
In the field of semiconductor fabrication, to form an interlayer insulator with a low dielectric constant, a method of fabricating a nanoparticle oxide thin film consisting of Silicon oxide (SiOx) by using evaporation of Si in an Oxygen-containing inert gas has already been proposed (Jpn. Pat. Appln. KOKAI Publication No. 11-289013). Compared to a nanoporous oxide thin film fabricated by the conventional method, a nanoparticle oxide thin film fabricated by this method can relize a low dielectric constant even with a low porosity.
More specifically, an SiOx nanoparticle thin film fabricated by the gas evaporation method as described above has the following structure and properties.
This SiOx nanoparticle thin film is expected to have a low dielectric constant because it is made of nanoparticles and the air around them. Since the film is a Silicon oxide film, it does not easily allow any ionized metals to pass through, so the insulation properties are less likely to deteriorate. As the film is a Silicon oxide film, its high-temperature stability is high. Since the film is fabricated by the gas evaportation method, the number of fabrication steps remains the same as that of the present method, so the cost preformance is high. Compared to a porous oxide thin film fabricated by some other method and having an equivalent dielectric constant, the film has a low moisture absorption although it is porous, because its voids are closed.
Unfortunately, the fabrication of this SiOx nanoparticle thin film by the gas evaporation method has the following problems. The condition of the gas evaporation method generally used as a nanoparticle formation method is that nanoparticles formed using an inert gas do not react with the ambient gas. In the fabrication of an SiOx nanoparticle thin film, however, Oxygen must be mixed in the ambient gas in order to entrap this Oxygen into nanoparticles. Since the ambient gas reacts with the nanoparticles unlike in the original gas evaporation method, the particle size of the nanoparticles is difficult to control, and the reproducibility of the particle size also worsens. The difficulty in control of the particle size of the nanoparticles deegrades the reproducibility of porosity and that of the dielectric constant based on the porosity of the SiOx nanoparticle thin film fabricated.
As described above, a method of fabricating an Si nanoparticle oxide thin film by the gas evaporation method using an Oxygen-containing inert gas can be used to form a low-dielectric-constant interlayer insulator. However, this method has the problem that the particle size of the nanoparticles is difficult to control, and the reproducibility of the porosity and dielectric constant is low.